The present invention relates to electrical coils consisting of a spool-like bobbin of molded plastic insulating material having many turns of fine wire wound thereon with a pair of terminal leads connected to opposite ends of the wire.
Since the field coil wire is very fine, on the order of 0.1 millimeter in diameter, one of the most difficult steps in the manufacture of electrical coils is the attachment of the fine wire to the larger lead wire and also maintaining the lead wire in a fixed position with respect to the bobbin.
Normally this is accomplished by utilizing a separate element or lug that is especially configured to receive a terminal lead. Examples of such devices are disclosed in Foerster U.S. Pat. No. 3,359,520 and Dumeige U.S. Pat. No. 3,609,616. While this type of separate element provides a secure connection for connecting terminal leads to a bobbin structure, the overall cost of assembling such a unit is extremely high since the lugs must be manufactured separately and then attached to the bobbin structure.
Attempts have been made to provide a connection between the lead wire and the field coil wire which do not require separate elements. Examples of this type of connection are shown in Biesma et al. U.S. Pat. No. 3,315,198; Davis U.S. Pat. No. 3,544,940; and Davis U.S. Pat. No. 3,660,791.
While these types of connections may be satisfactory in terms of providing a rigid securement of the terminal leads to the ends of the fine wire, difficulties have been encountered in utilizing such connecting means on automatic winding machinery since they either require the use of the separate element or many complicated steps in producing the connection.